Initial pin states after power up (ESP32-S2)

[T94T]

CircuitPython version

Adafruit CircuitPython v8.1.0 available from official download page
and
Custom compiled Adafruit CircuitPython v8.2.0

Code/REPL

# no custom code (just the factory default code.py file)

Description

I have noticed that all pins output 3.3V after a power up. Presumably the internal pull-ups have been activated by default. So I ask here where this is defined in the source code of CircuitPython. Is this intentional or a bug?

This is my setup and procedure:
Hardware: Lolin S2 Mini (based on ESP32-S2FN4R2)

Step 1: Uploaded an "empty" script compiled with arduino-esp32 (v2.0.6) and all pins remained in input state (0V).
Step 2: Burned the TinyUF2 bootloader. The board stays in DFU mode and all pins remain in input state (0 V).
Step 3: Uploaded CircuitPython (UF2 binary, v8.1.0 and also custom compiled v8.2.0). After reset and waiting for CircuitPython to fully boot, all pins output 3.3V.

Additional information / Update

I tried the above with an ESP32-S3-DevKitM-1-N8R2 with exactly the same behaviour.

[dhalbert]

The default pin reset code provided by the ESP-IDF resets the pins with pull-up (instead of floating). According to the documentation, this minimizes power consumption. It also prevents glitches on external pins that might trigger NeoPixels, etc. This is discussed in the comments in #5931.

[T94T]

@dhalbert, thank you for pointing me to the right direction. This is not good because the board always goes into DFU mode on single reset if DOUBLE_RESET_RC has been activated when using the TinyUF2 bootloader (https://github.com/adafruit/tinyuf2/tree/master/ports/espressif#usage). A simple but ugly workaround will be to set the PIN_DOUBLE_RESET_RC as an input pin in code.py (or main.py)

[jepler]

In CircuitPython espressif port, we have a special case for what Adafruit terms the "double tap pin":

// _reset_pin in common-hal/microcontroller/Pin.c
    #ifdef DOUBLE_TAP_PIN
    // Pull the double tap pin down so that resets come back to CircuitPython.
    pull_down = pull_down || pin_number == DOUBLE_TAP_PIN->number;
    #endif

I do not know if this is equivalent to the functionality on this board; there's also espressif_board_reset_pin_number which allows a particular board to override how a particular pin is set when not otherwise in use.

[T94T]

Amazing, thanks so much for the in-depth look at this issue.

[dhalbert]

@T94T is the DOUBLE_TAP_PIN definition missing from this particular board? If so, that would fix the problem, I think.

[T94T]

Ok, got it. The DOUBLE_TAP_PIN definition needs to be set in the board's mpconfigboard.h file. Thank you very much!